Coaxial In and Out on a Receiver: The Digital Loop Explained

Many receivers, soundbars and audio processors show a pair of ports: ‘coaxial in’ and ‘coaxial out’. Wired together in sequence, they form a digital pass-through chain that carries one audio stream through several devices, each of which can decode its own copy while forwarding the untouched bit stream. This guide explains how the loop works, the wiring for a two- and three-device chain, the settings that keep it clean, and the failure modes – because a coaxial chain is only as strong as its weakest termination.

Quick Answer

Coaxial in/out chaining works like this: source to device A’s coaxial in; device A’s coaxial out to device B’s coaxial in, and so on. Each device can decode locally while passing the original bit stream onward, provided its output is set to pass-through (not PCM-decoded) when the next device should do the decoding. Use 75 ohm S/PDIF coax between links, keep each link short, and terminate cleanly – a mismatched or loose link injects bit errors that show up as crackle or format dropouts on the last device in the chain.

How the Coaxial In/Out Loop Works

The ‘coaxial out’ on a modern receiver is, electrically, a repeat of whatever arrived at ‘coaxial in’ – a clean S/PDIF re-transmission, not a mixed or processed signal. That is what makes the loop possible: the stream passes through the device untouched while the device’s own decoder uses a local copy. The catch is the device’s output mode menu. In pass-through mode it forwards the original encoded stream (the next device decodes 5.1). In PCM mode it decodes internally and forwards only stereo – the next device hears music, not surround. Getting that one setting right is the whole game of chain wiring.

Pass-through vs decoded output

Pass-through: bits in, bits out, same format – use when the next device has a decoder and should own it. Decoded/PCM: the device converts to stereo PCM before forwarding – use when the next device is a DAC or simple amp that cannot decode. Some devices auto-select; most do not, so set it explicitly and note it in the install.

Wiring a Two-Device Chain

The most common real chain is TV to AV receiver to DAC. Cable one: 75 ohm digital coax from the TV’s coaxial out to the receiver’s coaxial in. Cable two: 75 ohm digital coax from the receiver’s coaxial out to the DAC’s coaxial in. The receiver’s coax output must be set to pass-through for 5.1 content (the receiver decodes for its own speakers and forwards for the DAC’s path), or to PCM if the DAC path is the only one you care about. For the port-level spec on both ends, see our coaxial output guide, and the input-side view in coaxial digital inputs.

Settings That Keep the Chain Clean

Four settings matter, in order. One: each middle device’s coax output mode – pass-through for encoded content. Two: sample rate consistency – if the TV sends 96 kHz PCM, every device in the chain must accept it; when in doubt, lock the source to 48 kHz. Three: the last device’s input selection – it must be pointed at its coax input, not optical. Four: decoder enablement on each unit that should decode. After any change, power-cycle the chain from the last device upstream; format detection happens at boot on most units, and a chain that ‘works but drops out’ is almost always a device that detected the format before the upstream change landed.

When the Loop Fails

Failure one: bit errors on the last device – a loose RCA, a marginal cable, or a cheap Y-split tapping the line (splitting S/PDIF with a passive Y is not recommended; each tap loads the line). Failure two: format mismatch – the chain is set to forward 96 kHz into a 48 kHz-only device; lock the rate. Failure three: decoded output where pass-through was intended – the symptom is ‘5.1 became stereo at device B’. Failure four: cumulative length – each link adds reflection risk; past about 15 m of total chain, upgrade the cable build rather than adding devices. Isolate by listening at each hop: a chain that is clean at A and noisy at B blames the A-to-B cable, not the equipment.

Coaxial In/Out Chain Scenarios

Real-World Applications

Coaxial in/out loops appear where one digital source must feed several destinations: a multi-zone home where the main receiver’s pass-through feeds a kitchen amp and a garage amp in series; a listening room where the AV receiver’s coax out feeds a dedicated DAC for the front pair while the receiver drives the surrounds; a commercial multi-room install where a rack processor chains zone amps; a test bench where the loop lets instruments sit in the signal path; a home cinema where the subwoofer’s digital input hangs off the receiver’s coax out; and a retrofit where a legacy receiver with in/out ports extends a modern source’s reach. The pattern is always the same: one stream, several decoders, clean terminations, and one pass-through setting per hop.

Related Guides

• CoaxialOutput
• CoaxialDigitalInputs
• Cable selection FAQ

Frequently Asked Questions

Can I daisy-chain many devices on coaxial in/out?

Yes, but each hop adds reflection and fault risk. Keep the total run under about 15 meters, limit the chain to two or three devices, and use quality 75 ohm cable with clean terminations at every point.

Do I set the middle device to PCM or bitstream?

Bitstream (pass-through) if the next device should decode the surround. PCM if the next device is a DAC or simple amp that only plays stereo. The choice is about who decodes, not about quality.

Is the coaxial out a perfect repeat of the input?

On most consumer receivers, yes – it is a clean pass-through re-transmission. Some units insert processing (EQ, downmix) if you enable it; leave the path untouched and the bits arrive as they left.

Why does the last device in the chain drop out intermittently?

Usually a marginal link: a loose RCA, a cheap cable, or a passive Y-split loading the line. Check terminations at every hop first, then replace the last cable segment – the symptom tracks the weakest joint, not the equipment.